I have a hexagon-shaped 55 gallon tank that has housed lots of healthy fish for about a year. Before Thanksgiving, I changed most of the water with the fish still in it. The next day, my 6" long Bala Shark went down. He was belly-up on the bottom, but still kicking around. I didn't have an isolation tank, so I just waited to see if he would recover. On Thanksgiving morning, I woke up to find he was right-side up again hanging around the middle of the tank. "What a miracle!" I thought. Within a few days, I started seeing white spots on my other fish. I recalled that my red-finned shark has always scratched himself on ornaments from time to time, so I diagnosed this as ich. I bought some Jungle brand ich treatment at my local store and dosed the tank carefully: 5 teaspoons. Within a couple of hours, one of my hatchetfish was dead. The next morning, the other one was too-- along with some other fish. In all I lost 2 hatchetfish, 3 small balas, (these were intended to replace the big one when he went down) an African brown knife, and 3 tiger barbs. All I have left now are my 6" red-finned shark, 2 red fire gouramis and a tough little catfish. Throughout all this death and chaos, none of these survivors showed any symptoms or ill effects from the malachite green. Now I am starting to see white spots on the head of my red-finned shark, and he obviously isn't feeling well. He stays in a castle/cave a lot, but he would always come out in the past to munch on some algae. Lately he has stayed holed up. What is this disease killing my fish? I guess it attacks the species that are easiest for it to affect first, then moves on to the bigger challenges. Why are the gouramis not affected? I ordered some Rid-ich from petmountain. I think I need to go get some melafix and a small isolation tank to put these remaining fish in while I thoroughly clean the 55-gallon. Help please! What else should I do?

if it is ich crank the heat up to 85 or a little over and salt the tank with aquarium salt, that will cycle the parasites life over 3-4 days, and the parasite should drop off the fish if my understanding is correct, leave it up at 85 for a couple of weeks an a bit that should end up killing off the parasite. the meds can cause more harm than good from what im told, it will kill your plants unless you get the specific ones that are plant friendly, the jbl is apparently cancerous, not sure about others so dont put ur hands in the water...

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190L corner with a variety of fish i will not mention as its ever changing and i cant be bothered to keep editing a sig

Swimming funny after a big water change can mean you dropped to "salt" level in the water too quickly. Getting ich after a big water change means the fish got cold. Despite the fact the ich reproduce faster in warmer water, a sudden temp. drop can trigger an ich in fish that have been healthy for years.

Search for old threads there are several ways to treat ich. Heat and salt, a good ich med, or even moving fish from container to container. All the methods work most of the time if the fish aren't too far gone, but there are strains of ich resistant to each med and even salt. I tend to use "quick-cure" for ich just because I have it handy and it easy to dose. It dose stain stuff. Most any med will work if used as directed for the whole time period or longer. Signs of ich maybe gone in 3 day but it can take 3 weeks or longer to kill all the ich. Some fish can't take heat, some can't take salt, some can't take formalin or other mes, so pick a treatment that suits your fish. Melafix and stuff that "prevents" ich are more like vitamins than medicine. Get something strong if fish are dying and check if your heater is working.

Thanks guys. I just ordered a larger heater and air pump to aerate both the 55-gallon and the isolation tanks. I got free shipping on a $49 order at petmountain. Do you guys already have a supplies advertiser? That site has the best prices I have seen.
I got a 1-gallon hospital tank today. Do you think that would be too small for my red-finned shark? He may be more like 8 inches from nose to tail fin. I hate to subject the goramis to heat and salt if they don't need it. I could put them and the catfish in the smaller tank, and treat the big tank with the shark alone in it. I want to empty it completely and clean it real well. Would it help to put the gravel in boiling water?

does sound like they need oxygen if all the fish are doing it, its not silly cos gills can on lots of fish
if you go for the major clean you are going to do you will kill all of your good bacteria and will need to cycle your tank again which could do them more harm than they are suffering with now.http://www.waterlife.co.uk/waterlife/chart.htm
this may help you understand a little more about what could be wrong, it may be something other than ich and you could be trying to treat for the wrong thing

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190L corner with a variety of fish i will not mention as its ever changing and i cant be bothered to keep editing a sig